1. Field of the Invention
The present invention relates to an apparatus and a method of providing a Quality of Service (QoS) for a multi protocol label switching (MPLS) traffic.
2. Description of the Related Art
Recently, as the number of Internet subscribers has exponentially increased, the subscribers have demanded various services requiring a QoS with respect to a voice, a moving picture, etc. on the Internet as well as data transmission on a best-effort service, which distinguishes the Internet.
The Internet is a technology suitable to a general data transmission such as a file transmission protocol (FTP) and is mainly based on the Ethernet. An MPLS was developed in order to satisfy the subscribers' demand such as a real time data transmission in the Internet environment.
The MPLS is a protocol between 2 layer and 3 layer of a communication protocol. In the MPLS, a label of 2 layer is recorded in a head of a packet, and data is transmitted in transmitting the packet by using just the label recorded in MPLS header information of the packet. Therefore, the packet can be transmitted to its destination at high speed without operating towards 3 layer. That is, the MPLS classifies a forwarding equivalence class (FEC) using the same destination IP address as a key, based on a forwarding table generated by a general routing protocol, and gives the same label to a routing entry included in the same FEC. Therefore, packets having the same destination have the same label, and thus are transmitted to their destination at high speed by label switching.
In the MPLS, a path is established for transmission and reception, the path is called a label switching path (LSP). The LSP is connection oriented such that the Internet traffic is transmitted in real time. The protocol for the label switching may include a border gateway protocol (BGP) or a label distribution protocol, etc.
An MPLS router located in an MPLS network establishes the LSP using a label included in a shim header for the label switching, and transmits the packet using the label in the MPLS network area. At this point, the MPLS shim header includes 20-bit label field, 30-bit experimental (EXP) field (or a class of service (CoS) field), 1-bit stack field, and 8-bit time to live (TTL) field.
The MPLS router classifies classes by each EXP regardless of the LSP, and provides different QoS to each of the classified classes. That is, the MPLS router classifies the classes by each EXP regardless of the LSP, and provides the QoS to the aggregated traffic of the packets having the same EXP value. In other words, when the packets in different LSPs have the same EXP value, the packets are treated as a same aggregated class, and QoS can be applied only to the aggregated class.
Accordingly, when the packets having the same EXP are received from different LSPs, different QoS cannot be provided to the packets according to each of different LSPs.